1. Field of the Invention
The present invention relates to a blanking device for blanking multiple charged particle beams, and more specifically, to a blanking device in multi beam writing, for example.
2. Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. The electron beam (EB) writing technique, which intrinsically has excellent resolution, is used for writing or “drawing” a pattern on a wafer and the like with electron beams.
As an example employing the electron beam writing technique, a writing apparatus using multiple beams (multi-beams) can be cited. Compared with the case of writing a pattern by using a single electron beam, since it is possible to emit multiple beams at a time in multiple writing, the throughput can be greatly increased. For example, in the writing apparatus employing a multi-beam system, multiple beams are formed by letting an electron beam emitted from an electron gun assembly pass through a mask with a plurality of holes, blanking control is performed for each of the beams, and each unblocked beam is reduced by an optical system and deflected by a deflector so as to irradiate a desired position on a target object or “sample”.
In multi-beam writing, the dose of each beam is individually controlled based on an irradiation time. For highly accurately controlling such a dose of each beam, it is necessary to perform blanking control to provide on or off of a beam at high speed. In a writing apparatus of a multi-beam system, a blanking control circuit for each beam is placed on a blanking plate where each blanker for use in multiple beams is arranged. It has been considered to respectively embed a shift register in the control circuit for each beam and to output a signal from a pad to shift registers connected in series in each row, in a plurality of blankers arranged in a matrix. In order to execute the contents of the consideration, pads whose number is the same as that of the rows of a plurality of blankers need to be located at the blanking plate. On the other hand, for suppressing a signal delay, it is desirable for the length of wiring from each pad to the shift register at the end of corresponding shift registers connected in series, to be equal to each other. Therefore, it has been examined to arrange each pad at a beam pitch at one of the four sides of a quadrangular region where a plurality of blankers are arranged in a matrix. In that case, since each blanker and each control circuit arranged at the blanking plate are manufactured using the LSI manufacturing technology, there is an upper limit for the chip size, which is about 20 mm. Therefore, if the number of beams increases and thus the number of rows increases, it becomes difficult to arrange pads, whose number is corresponding to the number of the rows, at one side of the blanking plate. For example, assuming that the beam arrangement is 512×512, the beam pitch is about 32 μm and thus the distance between pads becomes too narrow to arrange the pads.
Moreover, when the number of beams increases, the number of shift registers arranged in one row also increases. Therefore, data transmission will take time. The number of shift registers connected in series needs to be decreased in order to perform a high-speed operation, but, if the number of shift registers connected in series is reduced, the number of pads will increase. Thereby, it becomes further difficult to arrange the pads.
Furthermore, although differing from the case where data transmission is performed using a shift register, there has conventionally been considered a blanking plate in which electrode pads, whose number is the same as that of blankers, are arranged so as to surround the blankers (blanking electrodes) for use in multiple beams (e.g., refer to Japanese Published Unexamined Patent Application (JP-A) No. 11-176719). According to this technique, a deflection voltage is directly applied to the electrode of each blanker from the pad.